Project #44892 - Combinatorial probability

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1. Of 12 patients, 7 have a positive test result and 5 have a negative test result. IF 3 patients are selected at random from the 12 patients, what is the probability that none of them will have positive results?

2. A drug is expected to have positive results in 50% of the cases. If 12 patients are treated with the drug, what is the chance that at most 2 will have positive results. Obtain an answer using the normal approximation with correction for continuity.

3. For the experiment in (2), there were 2 patients of the 12 with postiive test results. Explain how this provides evidence that the drug has positive results in less than 50% of cases